I'm not answering your question.....but I have found a VERY EASY way to double click. I used to try and just do it like would first make sense, touch relese (about a half an inch away) and then click again. It is very hard to do it this way because you can't hit it at the same time all off the time. What i figured out is if you "press" on the screen and release presure (but don't take your finger off the screen) and then apply pressure again, it is very easy and works every time for me. Just thought I'd share this knowledge.
Dont click release click, click release pressure and then apply pressure again.